Our increased understanding of the processes of diffusion and dissemination of effective prevention interventions has lead to keener recognition of the need for focus on the related but unique issues of implementation of effective interventions. Central among the issues to be addressed in implementation research is better understanding of the relationship between fidelity of implementation of the original intervention with replication (retention) of the effective outcomes of the original intervention. Over the past decade, the US-Bahamian team adapted an evidence-based program Focus on Youth with Informed Parents and Children Together from the CDC's Diffusion of Effective Behavioral Interventions (DEBI) portfolio to produce a 10-session adolescent HIV prevention program (with two additional follow-up booster sessions) entitled Focus on Youth in The Caribbean (FOYC) and a 1-hour parental monitoring intervention entitled Caribbean Informed Parents and Children Together (CImPACT)]. FOYC+CImPACT was evaluated through a randomized, controlled longitudinal trial involving 15 Bahamian elementary schools. Based on the effectiveness of FOYC through 36 months, the Bahamian Ministry of Education has decided to incorporate FOYC+CImPACT into the grade 6 curriculum throughout all 78 government elementary schools in The Bahamas, with follow-up booster sessions in grades 7 and 8. The proposed research will be conducted during the national implementation of FOYC+CImPACT. The research will enable us to refine and validate a definition of fidelity of implementation which can be used across the field of implementation science; to identify factors which impact fidelity of implementation; and, to test the relationship Following between fidelity of implementation and replication of intervention outcomes. pilot work among five elementary schools, the proposed implementation assessment will be conducted among the remaining 73 elementary schools in The Bahamas. Subjects will include ~ 300 grade 6, 7 and 8 teachers, ~ 140 principals and guidance counselors and ~4800 students in grade 6 at baseline and followed forward through grade 9. Through the use of observation forms assessing fidelity of implementation to be completed by trained observers, self-assessment forms to be completed by teachers, guidance counselors and principals assessing factors hypothesized to be related to fidelity of implementation, and a questionnaire assessing student outcomes (knowledge, skills, perceptions and behaviors), we will address: Aim 1: Assess the school level factors associated with fidelity of implementation of FOYC+CImPACT; Aim 2: Assess the classroom (teacher) level factors associated with fidelity of implementation of FOYC+CImPACT; Aim 3: Determine the relationship between delivery of FOYC+CImPACT with varying levels of fidelity and student outcomes including knowledge, skills, risk perceptions, intentions and behaviors; and, Aim 4 (secondary): Explore issues in the measurement of fidelity.